Abstract
Betaglycan is a type III TGF-β receptor that binds to both inhibin and TGF-β with high affinity and determines cellular sensitivity to these ligands. Previous studies have suggested that betaglycan acts as a tumour suppressor in certain human epithelial cancers. However, the roles of betaglycan in ovarian granulosa cell tumours (GCTs) are poorly understood. The objective of this study was to determine whether human GCTs exhibit betaglycan expression, and if so, what impact this receptor has on tumour biology. Real-time PCR was used to quantify betaglycan transcripts in human GCTs (n = 18) and normal premenopausal ovaries (n = 11). This analysis established that GCTs exhibited a significant 2-fold reduction in mean betaglycan mRNA levels as compared with the normal ovary (P < 0.05). Similarly, two human GCT cell lines, the KGN and COV434, exhibited low betaglycan expression and poor responsiveness to TGF-β and inhibin in luciferase reporter assays. Stable transfection of GCT cell lines with a wildtype betaglycan (WT-BG) expression plasmid conveyed ligand responsiveness. FACS analysis was used to examine cell cycle progression and cell death in the GCT cell lines. This analysis revealed that WT-BG had no effect on the number of cells cycling or undergoing apoptosis. However, WT-BG significantly increased the adhesion of COV434 (P < 0.05) and KGN (P < 0.0001) cells to collagen IV and fibronectin, decreased cellular invasion through Matrigel COV434 (50%) and KGN (75%), and inhibited wound healing COV434 (70%) and KGN (80%). Collectively, the data establish that betaglycan is an important regulator of granulosa cell biology and suggest that a deficiency in betaglycan contributes to the pathogenesis of granulosa cell cancer. The work further suggests a role for betaglycan in the prevention of tumour invasion, possibly by increasing the adhesion of granulosa cells to matrix components. Supported by: the NHMRC of Australia (RegKeys 338516; 241000; 441101; 388904).
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